The present invention relates to seismic data. More specifically the present invention relates to retrieving seismic data from a seismic section provided in the form of a scanned seismic profile in a binary image format (bitmap).
Seismic data has been collected for several decades and a vast part of the older seismic data is only available in paper format of seismic sections. According to conservative estimates there are several millions of paper seismic sections owned by oil companies and similar institutions, the value of which is huge and sometimes immeasurable, especially when surveys are no longer possible in certain areas.
With the introduction of modern seismic workstations and user friendly interpretation software, most of these paper seismic sections have become useless, unless they can be converted into digital format (e.g., into standard SEG-Y format). In current conversion technology, the conversion process is slow, due to large amount of manual intervention, and involves relatively high costs and long throughput times. The slow process and the high costs discourage many oil companies from converting the legacy paper seismic sections into SEG-Y. The conversion is currently done on a project by project basis, driven by opportunity or to fulfill legal obligations.
A seismic section typically includes seismic traces, which represent the responses of the elastic wavefield to the density of earth layers and acoustic velocity across these layers as acoustic energy travels from a source through these layers to one or more receivers. A seismic section paper is typically a large sheet of about 2-3 meters by 1 meter. It is composed of two main parts: metadata and traces. The metadata is a graphical and a textual data describing mainly acquisition parameters. The traces area, which is the largest part, is composed of a large series of a traces plotted one next to the other. A trace is a series of amplitudes at time steps (from top to bottom), around an imaginary base line. The traces appear as vertical wiggling lines (referred to as “wiggles”). Seismic sections sometimes include horizontal time lines (or depth lines if conversion from time to depth had been performed). In some seismic traces the positive or negative sides of the wiggles are blackened—areas to the right (for positive) or to the left (for negative) of the imaginary base line about which the line wiggles confined between the line and that base line appear as black blobs.
A snippet of a larger paper scanned image of a seismic section is shown in FIG. 1. Each vertical line represents a vertical function (and is called a wiggle). It is evident that digitizing this graphical representation is not an easy task. It is evident that the vertical lines in some cases overlap and it is hard to distinguish and determine the correct line. Furthermore, typically the right hand side of a wiggle has amplitude overlaps, which are characterized by black areas (blobs), that represent the area confined between the imaginary zero axis (also called “the base line”) and the function line when the value of the line is above zero.
This makes it extremely difficult to obtain information on the positive side (or negative, depending on the “blobbed” side) of the line functions, and it is, therefore, practically impossible to follow a function line that crosses a blob.
Another problem is image quality and in particular discontinued lines (mainly associated with scan quality).